A typical vertical reciprocating conveyor includes a carriage having a deck or platform to support cargo as the carriage is guided for vertical movement by an actuating mechanism in a shaft of a support frame that includes a set of vertical support columns interconnected by side guards, such as enclosure panels, walls or the like. A vertical reciprocating conveyor typically employs a movable door for gaining access to the carriage through a door opening, and an electromechanical door lock for controlling the opening and the closing of the door depending upon the vertical position of the carriage. The door lock normally operates to prevent the door from being opened unless the carriage is at a designated loading/unloading level, and also prevents carriage movement if any door is not fully closed or locked. The door lock is designed to maintain closure of the door to prevent against accidental falls of personnel, cargo and equipment into an open shaft of the support frame when the carriage has moved away from the designated loading/unloading level. In the event of failure of the door lock, such as caused by damage thereto or malfunction thereof, an undesired door opening can create a severe safety hazard, particularly in poorly lighted areas.
Therefore, it is desirable to provide an extra measure of protection for a door opening or frame on a vertical reciprocating conveyor in the form of a visual warning barrier that is automatically deployed across the door opening to warn against entry into an open shaft of a vertical reciprocating conveyor in the event of a failed door lock.